The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Catalytic converters are used in motor vehicles to react with and purify the hot exhaust gases discharged from an internal combustion engine. The catalytic converter typically includes a substrate, often constructed of a ceramic material, having channels or other flow conduits, such as honeycombs, for the passage of the hot exhaust gases. The substrate can be loaded with a catalyst which functions to purify the hydrocarbons (HC), carbon monoxide (CO) and nitric oxide (NOx) in the exhaust gases through a catalytic reaction process.
The catalytic converter can also include a housing having a central chamber, an inlet for receiving the hot exhaust gases, and an outlet for exhausting the purified gases. In most applications, the catalytic substrate is positioned within the control chamber for performing the gas purifying function. A support member, such as a mat or wire mesh, is often wrapped around the substrate for supporting the substrate with respect to the housing. The support member can be placed between the catalytic substrate and the housing and exert a radially-directed load to inhibit movement of the catalytic substrate and absorb shock. In some catalytic converters, laterally-spaced seal members can be disposed at opposite ends of the catalytic substrate, adjacent to the inlet and outlet ends of the control chamber, to reduce leakage of untreated exhaust gases and compensate for surface irregularities on or between the substrate and/or the chamber caused by flexibility of the support member.
Typical catalytic converters include a cylindrical catalyst-coated substrate having flat inlet and outlet surfaces which tend to exhibit uneven gas flow patterns across their entire planar face surface. As such, most of the hot exhaust gases are directed to flow through a central portion of the catalytic substrate. Unfortunately, this configuration may result in reduced efficiency of the catalytic function and reduced life expectancy of the catalytic converter.
A significant portion of the undesirable emissions exhausted from a vehicle's internal combustion engine occurs during the first few minutes of engine operation following a cold start. This is due to the fact that the catalytic converter is not optimally functional until the catalytic substrate reaches its working temperature, commonly referred to as achieving “light-off”. In view of stricter emissions regulations, it is critical to reduce the time it takes the catalytic converter to reach its working temperature.
Accordingly, a need exists for development of catalytic converters having quicker light-off characteristics and enhanced flow patterns through the catalytic substrate.